Somniosidae, D.S.Jordan, 1888

Elasmobranch, Its Implications For Global, Parasitology, Diversity And, Naylor, G. J. P., Sc, Caira, J. N., Ct, Jensen, K., Ks, Rosana, K. A. M., Fl, White, W. T., Csiro, Tas, Last, P. R., Csiro & Tas, 2012, A Dna Sequence-Based Approach To The Identification Of Shark And Ray Species And Its Implications For Global Elasmobranch Diversity And Parasitology, Bulletin of the American Museum of Natural History 2012 (367), pp. 1-262 : 62-63

Somniosidae (sleeper sharks), continued

Proscymnodon plunketi (plunket shark) ( fig. 45)

The 12 specimens of this species included in the analysis were all collected from New Zealand and thus represent the more eastern elements of the distribution of this species. Most of these specimens were identical in sequence, but one specimen differed from the others by one base.

Scymnodon ringens (knifetooth dogfish) ( fig. 45)

All five specimens identified as this species included in the analysis were collected from Ireland and thus represent the northeastern elements of the distribution of this species. These specimens were identical in sequence. They clustered most closely with specimens of P. plunketi ; the average of the pairwise differences between these two species was 59.1.

Centroselachus crepidater (longnose velvet dogfish)

( fig. 45)

The analysis included 27 specimens of this currently monotypic genus. These specimens were collected from the mid-Atlantic ridge, Madeira, Scotland, southern Africa, Tasman Sea, and New Zealand and thus represent only the western Pacific and eastern Atlantic portions of the distribution of this species. The specimen collected from the Tasman Sea came was from the Australian National Fish Collection (GN4940 5 ANFC H 4873-01). The two specimens from Madeira are deposited in the Museu de História Natural e Aquário in Funchal (GN6617 5 MMF 36134 and GN6618 5 MMF 36136). The analysis yielded are a single cluster and, in fact, several specimens from Madeira, Scotland, and New Zealand were identical in sequence. However, the range of pairwise differences among all 27 specimens was 0–17, with an average of 2.4.

Zameus squamulosus (velvet dogfish) ( fig. 45)

Four specimens identified as Zameus squamulosus were included in the analysis. Two were collected from southern Africa and two from Tasmania and thus represent only a portion of the southern hemisphere distribution of this essentially cosmopolitan species. The range in pairwise differences among specimens was 0–6 bases, with an average of 4.6. They clustered most closely with C. crepidater . The average of the pairwise differences between specimens of these two species was 107.3.

Centroscymnus sp. 1 ( fig. 45)

The analysis included a specimen collected from New Zealand, and preliminarily identified as Centroscymnus sp. by Di Tracey. This specimen clustered provisionally along with, but outside the group comprised of the two specimens of Zameus squamulosus and the 27 specimens of Centroselachus crepidater (well away from the specimens of the two species of Centroscymnus included in the analysis). The average of the pairwise differences between this specimen and those of Z. squamulosus was 166. The average of the pairwise differences between this specimen and those of C. crepidater was 160.7. We have referred to this specimen here as Centroscymnus sp. 1 . However, it should be noted that results from barcode (COI) data, which show similar results within the Somniosidae , include a clade consisting of Z. squamulosus , C. crepidater , and a single specimen of Scymnodalatias albicauda from New Zealand. Thus, it is highly likely that this species actually refers to S. albicauda , but additional samples are required to confirm this.

Somniosus microcephalus ( Greenland shark)

( fig. 45)

Four of the five specimens of this species included here came from the Northwest Territories in northern Canada, the remaining specimen was from the eastern Atlantic. Thus, our sample represents much of the breadth of the distribution of this species. The range in pairwise differences among specimens was 0–1.

Somniosus pacificus (Pacific sleeper shark) ( fig. 45)

All four specimens of this species included in the analysis were collected from Alaska and thus represent only the eastern Pacific elements of the distribution of this species, which also includes the western Pacific. The range in pairwise differences among these specimens was 0–2, with an average of 1.2. The average of the pairwise differences between specimens of this species and those of S. microcephalus was 9.2. This result is consistent with that of Murray et al. (2008) with respect to the distinction between the latter two species.

Somniosus rostratus (little sleeper shark) ( fig. 45)

The single specimen of this species included in the analysis was collected from the coast of France, and thus is representative of the eastern North Atlantic distribution of this species. The average of the pairwise differences between this specimen and the specimens comprising the cluster of S. microcephalus was 32.4, and between those comprising the cluster of S. pacificus was 32.8.